The present invention concerns optical systems wherein a light beam is deflected by the displacement of an element containing an interference pattern.
Many fields of technological endeavor use optical scanners to convert object outlines, bar codes, printed characters and the like to electrical signals for analysis or transmission. The single most common scan pattern for such applications is one or more straight lines which are focussed in a substantially flat object surface.
The prior art shows that simple, inexpensive and rugged optical scanners can be realized by rotating an optical interference pattern through a light beam from a coherent source, such as a laser. But conventional systems lose these inherent advantages in the process of constructing a complete, practical scanner system. Commonly assigned application Ser. No. 643,891, filed Dec. 23, 1975, by Pole, et al, for example, requires a strongly curved object surface. In many cases, of course, the object cannot be curved in this way; for example, where a bar code on a solid package is to be read. Commonly assigned application Ser. No. 644,679, filed Dec. 23, 1975, by Wollenmann, now U.S. Pat. No. 4,026,630, is capable of producing a scan pattern lying in a plane, but the individual lines of the pattern are curved within this plane. Although such curves may be made to approximate straight lines, other constraints on the scanner may preclude the achievement of sufficient accuracy. There are also rotating-hologram scanners whose geometry permits the generation of substantially straight-line scan patterns. Examples of such systems are shown in U.S. Pat. Nos. 3,619,033 to McMahon, 3,721,487 to Pieuchard, et al, 3,795,768 to Locke, 3,922,059 to Noguchi, 3,922,060 to Oosaka, et al and 3,940,202 to Kato, et al. Each of these systems, however, is inherently physically large, complex and/or requires precise adjustments.